In cassettes of conventional 35 mm film, such as manufactured by Eastman Kodak Company and Fuji Film Company, Ltd., the filmstrip is wound on a flanged spool which is rotatably supported within a cylindrical shell. A leading end section of the filmstrip, commonly referred to as a "film leader," protrudes from a light-trapped slit or mouth of a cassette shell. One end of the spool has a short axial extension which projects from the shell, enabling the spool to be turned by hand. If the spool is initially rotated in an unwinding direction, the film roll inside the shell will tend to expand radially since the inner edge of the filmstrip is attached to the spool, and the fogged leader section protruding from the slit will remain stationary. The film roll can expand radially until a non-slipping relation is established between its outermost convolution and the inner curved wall of the shell. Once this non-slipping relation exists, there is a binding effect between the film roll and the shell which prevents further rotation of the spool in the unwinding direction. Thus, rotation of the spool in the unwinding direction cannot serve to advance the filmstrip out of the shell, and it is necessary in the typical 35 mm camera to engage the protruding leader section to draw the filmstrip out of the shell.
In the advanced photo system, the filmstrip is also wound on a flanged spool. A lip portion extends axially and inwardly around the periphery of the each flange for providing a surface against which the film rests for containing it within the spool. The film is initially disposed entirely on the spool, and the cassette contains a light-tight slit through which the film eventually passes upon unwinding. The lip portion of each retaining piece is slightly deflected adjacent the light-tight opening for permitting the film to exit through the light-tight opening.
For unwinding the film to permit image capture, a cassette containing the spool is inserted into a camera and the spool is rotated, which obviously causes the film to rotate substantially simultaneously therewith. The leading edge of the film is then directed through the tight-tight opening.
Although the presently utilized methods and apparatuses for unwinding the film are without drawbacks, an alternative cassette configuration with fewer components is always desirable.
Consequently, a need exists for providing another film cassette configuration having automated film extension, while providing for construction from fewer components.